Hi all. I'm sadly getting ready to bring my tropicals in for the winter. This will be my 3rd year bringing them in. The amount of light and humidity I give them keeps them healthy and growing all winter long. My question is about the effect photoperiod has on growing trees indoors. How important is it to match the natural daylight hours? Is it ok to extend the hours under light to 15/16 a day? Or is it healthier to give them shorter days to slow growth a bit until spring?

As you and me are in similar geographical positions I'll share my experiences bringing in the Tropicals, which for me range from Bougey's to a couple different species of ficus. This year adds a large Brazillian Raintree and Acacia forrest to the mix.

I use no supplemental lighting and the trees seem to just slow down, some go semi-dormant, yet hold on to their leaves. Some respond by dropping leaves and re-growing new ones that are either better positioned to catch the weaker winter sunlight, or are just unnecessary.

One trick I do now is allow crazy growth from about late July all the way up until now for all the tropicals, then just as they are coming in for winter I give them a good hard prune, they will respond by replacing what has been lost with "indoor" foliage lets call it in the space of time remaining until say early december.... this trick helps stop the heavy leaf drop I was experiencing my first few winters a while back when the trees were brought in. The new foliage that grew out in front of the window after the prune stays throughout the rest of the winter. Helps keep things green when all around is white.

I suppose supplemental light would allow you to keep the trees growing but its hard to provide enough wattage to encourage desirable growth and not leggy week extension.

Surprisingly my trees all crammed in their 5x8 foot south window do keep growing throughout winter, just slower. They do very well actually.

Thanks for the reply Jay. I'll try that pruning trick. They all need a good pruning now anyway. Without your advice I might of held off thinking that a prune would weaken them but what you say makes sense, and they're all very healthy. As far as light goes, I live in an apartment with windows only on the east side, and my wife would never allow me to block what little light we get from them (insert emoticon of a whip). I have a 400 watt mh and 6 good 48 inch grow lights in a 5 x 4 foot area. The growth over the last couple winters has been quite compact.

I have a small collection of tropicals that I grow under fluorescents during the winter. They get almost no natural light. I leave the lights on for about 18 hours a day and that seems to work OK. You may not need as many hours if you've got the higher intensity MH light.

Thanks Chris. So guess I'll just keep doing what I've been doing the last few years. 15/16 hours of light a day. Just wanted to make sure that a long photoperiod in the winter wouldn't harm them over the long run.

mgallex wrote:Thanks Chris. So guess I'll just keep doing what I've been doing the last few years. 15/16 hours of light a day. Just wanted to make sure that a long photoperiod in the winter wouldn't harm them over the long run.

You could conceivably give them 24hrs but plants will take a rest regardless, even if they are in constant light, so give them 7hrs of dark and save on electricity...

I have some tropicals and several years ago i set up a little tent in the basement which has 48in tubes suspended from a pvc frame. it is covered on 3 sides with plastic which is taped to the pvc. The plants sit on a boot tray from the farm and home store which is ribbed so the pots don't sit in water. I have a very small electric fan on a timer to move the air but not enough to blow the thing over. The lights are on 16 hrs. and the fan is on for about 60 minutes per day. While the fan may be overkill I don't have a problem with fungus, mold or mildew and the humidity stays fairly high due to the tenting. It works for me as I had problems in the winter with the air being too dry and the leaves suffered as well as getting leggy growth from the short day length in the winter in our zone.

David D's set up is good, having air movement, just enough to make grassy leaves move a bit, is very beneficial to keeping down fungal and bacterial problems.

Studies have been done, (UW Madison Forest Products Lab for example) to some extent you can make up for lower light intensities with longer day length. If you are running less than 1000 Watt MH or HPS lamps, you are not getting anywhere near full sun, directly under a 400 watt MH or HPS lamp is giving near or under 50% the intensity of direct sunlight. So it is good one can make up for low intensities with longer day length. The same lab also published on maximum day length, they were using pines as the subject. The maximum benefit was at 18 hours day length. As day length went longer there were no further improvements and a small decline was noticed. At 24 hour day length, they noted a significant lessening of the benefit of longer than 12 hour day length under artificial light.

What does it mean for us? Run the lights for our trees at 18 hours, anything more than an 18 hour day length will be a waste of electricity. Less than 18 hours, you aren't getting all the benefit you could from the artificial light. Majority of tropical trees are not day length sensitive for timing their flowering. There are exceptions, one would have to do their home work. For just vegetative growth, a long photoperiod would seem beneficial.

Thanks David and Leo. I'll keep them on a longer day time them. Most are all just in development stage so vegetative growth is all I need. I do raise the humidity with trays and a humidifier. It gets super dry in our little apartment, esp. with the HID running. And I also keep a gentle breeze going for circulation. I was warned that my Sagertia theezans would suffer from lack of humidity, but it did just fine last year, placed just above the humidifier.

Note, to others running sub-tropical species. The comments above in particular were targeted at raising true tropical genera. There are many sub-tropical genera of trees and shrubs that do need a 'rest', but need to be above freezing. For the species that grow best with a 'rest', cooler temperatures and a day length shorter than 12 hours, say 6 to 8 hours, are of great benefit. DrGonzo and others have had threads on this type of winter rest care. So what I said about true tropical genera, (Ixora, Buccida, Ficus, etc) holds, and doesn't contradict what was mention for example in the thread about Serrissa.

About the air movement. In addition to keeping fungal and bacterial issues down as far as the leaves are concerned, air movement helps get oxygen down into the potting mix. Good bonsai soil is porous, air movement over the surface of the pot will help the mass of mix breath, resulting in healthier roots in spring.

Please bear with some background info to set the table for a further question about air circulation.

I have a small mylar tent housing a 200W 6400K CFL sunblaster. http://sunblasterlighting.com/125-200-watt-cfl-lamp.phpMy lights are set up on a timer [for consistency sake] and there is a small fan inside the tent.The bulb, being CFL, burns fairly cool, so the fan is purely for circulation purposes.I have the option to either plug it into the timer with the lights or run it independently of the timer.Being the sometimes forgetful piece of work that i am, "independent of the timer" would probably mean 24 hours a day.

Any thoughts/guidance as to the better choice [ie: fan 24 hours or only in tandem with lights] ?

In my light garden, I have roughly 1000 orchids and a few, maybe 6 or 8 tropical bonsai. I have 2 large fans and 3 or 4 smaller ones, all positioned so there is a circulation pattern, east along one wall, then north, then west along the next. On one wall there is an exhaust fan, on the opposite there is a window that is open most of the year, closed only in the coldest months of winter. My fans run 24 hours a day 365 days a year. The breeze is not real strong, but it is a definite light movement of air across everybody. I get good roots on the orchids, and the bonsai too.

So for anyone else I would recommend leaving the fans on 24 hours a day. Think about it, most of the trees we grow come from breezy open landscapes.

There are those that disagree on the importance of moving air, but I do have more than one horticulture award for growing specimen orchids. It really seems to work for me.